Rioting erupted in Kabul yesterday when two US embassy vehicles were set ablaze after one collided with a civilian car, killing a number of occupants, officials and witnesses said.

Television pictures showed the vehicles in flames and young Afghan men throwing stones at them and beating them with sticks and iron bars.

Nato's International Security Assistance Force (ISAF) said it had despatched a quick reaction force to the area, outside the American embassy and near US and Afghan army bases in the centre of the city.

An ISAF official said the vehicles involved belonged to the US embassy.

"We don't know yet how many people were killed in the accident," interior ministry spokesman Zemarai Bashery said.

Witnesses said four passengers in the civilian car died when it was hit by one of two armoured vehicles moving in convoy.

The US embassy in Kabul released a statement saying that "four US contract personnel" had been in the vehicle involved in the accident.

"We understand that the other car contained four Afghan passengers. We have also been informed that there were fatalities and serious injuries among the Afghans involved in the accident," it said, without further detail.

Police fired shots in the air to quell the violence, an AFP reporter witnessed.

Afghan security forces cordoned off the area, closing the road to Kabul's international airport, he said.

Local resident Saleh Ahmed said the accident happened when the civilian vehicle attempted to drive on to the main road from a side street and was hit by one of the two armoured vehicles.

"The civilian vehicle was trying to get into the main road when the two foreign vehicles hit it and killed all four occupants," he said.